Applause (Latin applaudere, to strike upon, clap) is primarily the expression of approval by the act of clapping, or striking the palms of the hands together, in order to create noise. Audiences usually applaud after a performance, such as a musical concert, speech, or play, as a sign of enjoyment and approval. In most countries audience members clap their hands at random to produce a constant noise. It tends to synchronize naturally to a weak degree; in Russia, Norway and many northern and eastern European countries synchronized clapping is more popular than random clapping. The age of the custom of applauding is uncertain, but it is widespread among human cultures. The variety of its forms is limited only by the capacity for devising means of making a noise (e.g., stomping of feet or rapping of fists or hands on a table). Within each culture, however, it is usually subject to conventions. The ancient Romans had a set rituals at public performances to express degrees of approval: snapping the finger and thumb, clapping with the flat or hollow palm, and waving the flap of the toga. Emperor Aurelian substituted the waving of napkins (orarium) that he had distributed to the Roman people for the toga flapping. In Roman theatre, at the close of the play, the chief actor called out "Valete et plaudite!", and the audience, guided by an unofficial choregus, chanted their approval antiphonally. This was often organized and paid for.